Add Bytes to Field union

To make logging bytestrings and binary more efficient, add a byte slice to the
Field union. This adds ~80ns to the `AddingFields` benchmarks, but saves an
allocation along a path that particularly performance-sensitive applications
will use.

field.go

@@ -39,7 +39,7 @@ func Skip() zapcore.Field {
 // zap's JSON encoder base64-encodes binary blobs. To log UTF-8 encoded text,
 // use ByteString.
 func Binary(key string, val []byte) zapcore.Field {
-	return zapcore.Field{Key: key, Type: zapcore.BinaryType, Interface: val}
+	return zapcore.Field{Key: key, Type: zapcore.BinaryType, Bytes: val}
 }
 
 // Bool constructs a field that carries a bool.
@@ -55,7 +55,7 @@ func Bool(key string, val bool) zapcore.Field {
 // To log opaque binary blobs (which aren't necessarily valid UTF-8), use
 // Binary.
 func ByteString(key string, val []byte) zapcore.Field {
-	return zapcore.Field{Key: key, Type: zapcore.ByteStringType, Interface: val}
+	return zapcore.Field{Key: key, Type: zapcore.ByteStringType, Bytes: val}
 }
 
 // Complex128 constructs a field that carries a complex number. Unlike most

field_test.go

@@ -71,10 +71,10 @@ func TestFieldConstructors(t *testing.T) {
 		expect zapcore.Field
 	}{
 		{"Skip", zapcore.Field{Type: zapcore.SkipType}, Skip()},
-		{"Binary", zapcore.Field{Key: "k", Type: zapcore.BinaryType, Interface: []byte("ab12")}, Binary("k", []byte("ab12"))},
+		{"Binary", zapcore.Field{Key: "k", Type: zapcore.BinaryType, Bytes: []byte("ab12")}, Binary("k", []byte("ab12"))},
 		{"Bool", zapcore.Field{Key: "k", Type: zapcore.BoolType, Integer: 1}, Bool("k", true)},
 		{"Bool", zapcore.Field{Key: "k", Type: zapcore.BoolType, Integer: 1}, Bool("k", true)},
-		{"ByteString", zapcore.Field{Key: "k", Type: zapcore.ByteStringType, Interface: []byte("ab12")}, ByteString("k", []byte("ab12"))},
+		{"ByteString", zapcore.Field{Key: "k", Type: zapcore.ByteStringType, Bytes: []byte("ab12")}, ByteString("k", []byte("ab12"))},
 		{"Complex128", zapcore.Field{Key: "k", Type: zapcore.Complex128Type, Interface: 1 + 2i}, Complex128("k", 1+2i)},
 		{"Complex64", zapcore.Field{Key: "k", Type: zapcore.Complex64Type, Interface: complex64(1 + 2i)}, Complex64("k", 1+2i)},
 		{"Duration", zapcore.Field{Key: "k", Type: zapcore.DurationType, Integer: 1}, Duration("k", 1)},

zapcore/field.go

@@ -97,6 +97,7 @@ type Field struct {
 	Type      FieldType
 	Integer   int64
 	String    string
+	Bytes     []byte
 	Interface interface{}
 }
 
@@ -111,11 +112,11 @@ func (f Field) AddTo(enc ObjectEncoder) {
 	case ObjectMarshalerType:
 		err = enc.AddObject(f.Key, f.Interface.(ObjectMarshaler))
 	case BinaryType:
-		enc.AddBinary(f.Key, f.Interface.([]byte))
+		enc.AddBinary(f.Key, f.Bytes)
 	case BoolType:
 		enc.AddBool(f.Key, f.Integer == 1)
 	case ByteStringType:
-		enc.AddByteString(f.Key, f.Interface.([]byte))
+		enc.AddByteString(f.Key, f.Bytes)
 	case Complex128Type:
 		enc.AddComplex128(f.Key, f.Interface.(complex128))
 	case Complex64Type:

zapcore/field_test.go

@@ -100,14 +100,15 @@ func TestFields(t *testing.T) {
 		t     FieldType
 		i     int64
 		s     string
+		b     []byte
 		iface interface{}
 		want  interface{}
 	}{
 		{t: ArrayMarshalerType, iface: users(2), want: []interface{}{"user", "user"}},
 		{t: ObjectMarshalerType, iface: users(2), want: map[string]interface{}{"users": 2}},
-		{t: BinaryType, iface: []byte("foo"), want: []byte("foo")},
+		{t: BinaryType, b: []byte("foo"), want: []byte("foo")},
+		{t: ByteStringType, b: []byte("foo"), want: []byte("foo")},
 		{t: BoolType, i: 0, want: false},
-		{t: ByteStringType, iface: []byte("foo"), want: []byte("foo")},
 		{t: Complex128Type, iface: 1 + 2i, want: 1 + 2i},
 		{t: Complex64Type, iface: complex64(1 + 2i), want: complex64(1 + 2i)},
 		{t: DurationType, i: 1000, want: time.Microsecond},
@@ -133,7 +134,7 @@ func TestFields(t *testing.T) {
 
 	for _, tt := range tests {
 		enc := NewMapObjectEncoder()
-		f := Field{Key: "k", Type: tt.t, Integer: tt.i, Interface: tt.iface, String: tt.s}
+		f := Field{Key: "k", Type: tt.t, Integer: tt.i, Interface: tt.iface, Bytes: tt.b, String: tt.s}
 		f.AddTo(enc)
 		assert.Equal(t, tt.want, enc.Fields["k"], "Unexpected output from field %+v.", f)